I'm wondering if I have 1987 Donruss card variations that need to be added to the database or if they would be considered errors.

The back of the cards are printed upside down compared to the other cards.  In other words, if the front of the cards are all facing the same way, the back of these are upside down.

2 Eric Bell
133 Mike Davis
158 Carney Lansford
178 Eric Plunk
221 Steve Ontiveros
226 Chris Codiroli
282 Jay Tibbs (I have 1 card printed in each direction)
349 Mickey Tettleton
405 Donnie Hill
467 Jerry Willard
472 Dave Leiper
504 Tom Foley
528 Moose Haas
529 Wilfredo Tejada

I also have 45 Ozzie Virgil from the Opening Day set which is printed this way.

Tony, here's the info. 

1987 Donruss

Card backs are available in two distinct orientations. Cards from wax packs have their numbers in the upper right corner when the card is turned over while cards from the factory sets have them in the lower left.

Check out the Release Notes for the set here. I'm guessing you probably have the Factory Set variation. I believe the plan is to add the Factory Set as a parallel release once the current project(s) get wrapped up (I believe 1988 Donruss is still on-going).

There have been many threads on this.  The factory sets were all printed in this fashion, reverse of what the cards in packs were.  Because there is no visible difference to show in scans, this "VAR" will probably not be documented here by a separate set listed.

Oh, that's right - the 1988 parallel issue was because of border differences, not back orientation, wasn't it?

Font differences on the back for 88D, some cards also have border variations.

As Kyle notes, there were multiple differences in 1988.

There are no differences between factory and packed out in 1987 other than the orientation of the backs. There are zero plans of adding another whole set because the backs are oriented differently. There was no type-setting change. There was no border change. Additionally, this orientation difference does NOT affect the entire set as the Diamond Kings and checklists remain as is.

If you wish to catalog them here, add a comment in the Detailed Add.

I edited my post to include all the cards I have in this fasion.  Thanks for all the replies.

A funny (in retrospect) story about the 1987 Donruss backs: Around 2006-07 when Barry Bonds rookie cards were red hot, I was at a show where a dealer had a stack of about 10 of them out of the 1987 Donruss. A customer made a deal and bought all of them. About an hour later, I hear the customer screaming at the dealer, claiming they were counterfeit. The dealer was dumbfounded. 

I was standing a few tables down and I overheard the customer yelling about the back of the cards. I always knew the factory backs were reversed, so I walked over and explained the situation. The dealer had no idea and neither did the customer. Unfortunately the customer didn't believe me and kept screaming for his money back. I told them both if they could wait until the next day, I would bring my factory set to the show and show them (this was still pre-smart phones, so there was no other way to show them). Sure enough, I did, and everyone was satisfied. The dealer let me pick $20 of merchandise for free for helping him out of the mess. It pays to know your cards!